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i#6444 no exit: Dump rseq buffer on mid-region thread end
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If the thread trace ends mid-rseq-region, dump the buffer instead of
losing not only the rseq sequence so far but also the thread exit
record.

Adds a unit test.  Also tested on a real trace with this issue.

Fixes #6444
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@derekbruening
derekbruening committed Nov 10, 2023
1 parent 969e20d commit b6a5573
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Showing 2 changed files with 85 additions and 3 deletions.
80 changes: 78 additions & 2 deletions clients/drcachesim/tests/raw2trace_unit_tests.cpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1984,6 +1984,82 @@ test_rseq_side_exit_inverted_with_timestamp(void *drcontext)
check_entry(entries, idx, TRACE_TYPE_FOOTER, -1));
}

/* Tests a trace ending mid-rseq (i#6444). */
bool
test_midrseq_end(void *drcontext)
{
std::cerr << "\n===============\nTesting mid-rseq trace end\n";
instrlist_t *ilist = instrlist_create(drcontext);
instr_t *nop = XINST_CREATE_nop(drcontext);
instr_t *move1 =
XINST_CREATE_move(drcontext, opnd_create_reg(REG1), opnd_create_reg(REG2));
instr_t *move2 =
XINST_CREATE_move(drcontext, opnd_create_reg(REG1), opnd_create_reg(REG2));
instr_t *jcc =
XINST_CREATE_jump_cond(drcontext, DR_PRED_EQ, opnd_create_instr(move2));
instr_t *store =
XINST_CREATE_store(drcontext, OPND_CREATE_MEMPTR(REG2, 0), opnd_create_reg(REG1));
instr_t *move3 =
XINST_CREATE_move(drcontext, opnd_create_reg(REG1), opnd_create_reg(REG2));
instrlist_append(ilist, nop);
instrlist_append(ilist, move1);
instrlist_append(ilist, jcc);
instrlist_append(ilist, store);
instrlist_append(ilist, move2);
instrlist_append(ilist, move3);
size_t offs_nop = 0;
size_t offs_move1 = offs_nop + instr_length(drcontext, nop);
size_t offs_jcc = offs_move1 + instr_length(drcontext, move1);
size_t offs_store = offs_jcc + instr_length(drcontext, jcc);
size_t offs_move2 = offs_store + instr_length(drcontext, store);
size_t offs_move3 = offs_move2 + instr_length(drcontext, move2);

std::vector<offline_entry_t> raw;
raw.push_back(make_header());
raw.push_back(make_tid());
raw.push_back(make_pid());
raw.push_back(make_line_size());
raw.push_back(make_timestamp());
raw.push_back(make_core());
raw.push_back(make_marker(TRACE_MARKER_TYPE_RSEQ_ENTRY, offs_move3));
raw.push_back(make_block(offs_move1, 2));
raw.push_back(make_block(offs_store, 1));
raw.push_back(make_memref(42));
raw.push_back(make_exit());

std::vector<uint64_t> stats;
std::vector<trace_entry_t> entries;
if (!run_raw2trace(drcontext, raw, ilist, entries, &stats))
return false;
int idx = 0;
return (
check_entry(entries, idx, TRACE_TYPE_HEADER, -1) &&
check_entry(entries, idx, TRACE_TYPE_MARKER, TRACE_MARKER_TYPE_VERSION) &&
check_entry(entries, idx, TRACE_TYPE_MARKER, TRACE_MARKER_TYPE_FILETYPE) &&
check_entry(entries, idx, TRACE_TYPE_THREAD, -1) &&
check_entry(entries, idx, TRACE_TYPE_PID, -1) &&
check_entry(entries, idx, TRACE_TYPE_MARKER, TRACE_MARKER_TYPE_CACHE_LINE_SIZE) &&
check_entry(entries, idx, TRACE_TYPE_MARKER,
TRACE_MARKER_TYPE_CHUNK_INSTR_COUNT) &&
check_entry(entries, idx, TRACE_TYPE_MARKER, TRACE_MARKER_TYPE_TIMESTAMP) &&
check_entry(entries, idx, TRACE_TYPE_MARKER, TRACE_MARKER_TYPE_CPU_ID) &&
check_entry(entries, idx, TRACE_TYPE_MARKER, TRACE_MARKER_TYPE_RSEQ_ENTRY) &&
check_entry(entries, idx, TRACE_TYPE_ENCODING, -1) &&
check_entry(entries, idx, TRACE_TYPE_INSTR, -1, offs_move1) &&
check_entry(entries, idx, TRACE_TYPE_ENCODING, -1) &&
#ifdef X86_32
// An extra encoding entry is needed.
check_entry(entries, idx, TRACE_TYPE_ENCODING, -1) &&
#endif
check_entry(entries, idx, TRACE_TYPE_INSTR_UNTAKEN_JUMP, -1, offs_jcc) &&
check_entry(entries, idx, TRACE_TYPE_ENCODING, -1) &&
check_entry(entries, idx, TRACE_TYPE_INSTR, -1, offs_store) &&
check_entry(entries, idx, TRACE_TYPE_WRITE, -1) &&
// The trace exits before it reaches the rseq endpoint.
check_entry(entries, idx, TRACE_TYPE_THREAD_EXIT, -1) &&
check_entry(entries, idx, TRACE_TYPE_FOOTER, -1));
}

/* Tests pre-OFFLINE_FILE_VERSION_XFER_ABS_PC (module offset) handling. */
bool
test_xfer_modoffs(void *drcontext)
Expand Down Expand Up @@ -2666,8 +2742,8 @@ test_main(int argc, const char *argv[])
!test_rseq_side_exit_signal(drcontext) ||
!test_rseq_side_exit_inverted(drcontext) ||
!test_rseq_side_exit_inverted_with_timestamp(drcontext) ||
!test_xfer_modoffs(drcontext) || !test_xfer_absolute(drcontext) ||
!test_branch_decoration(drcontext) ||
!test_midrseq_end(drcontext) || !test_xfer_modoffs(drcontext) ||
!test_xfer_absolute(drcontext) || !test_branch_decoration(drcontext) ||
!test_stats_timestamp_instr_count(drcontext) ||
!test_is_maybe_blocking_syscall(drcontext))
return 1;
Expand Down
8 changes: 7 additions & 1 deletion clients/drcachesim/tracer/raw2trace.cpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -573,6 +573,11 @@ raw2trace_t::process_offline_entry(raw2trace_thread_data_t *tdata,
tdata->error = "Missing thread id";
return false;
}
if (tdata->rseq_buffering_enabled_ &&
// Deliberately pass 0 as the PC so it's treated as an instru
// exit and we just dump the buffer as-is.
!adjust_and_emit_rseq_buffer(tdata, 0, 0))
return false;
log(2, "Thread %d exit\n", (uint)tid);
buf += trace_metadata_writer_t::write_thread_exit(buf, tid);
*end_of_record = true;
Expand Down Expand Up @@ -2321,7 +2326,8 @@ raw2trace_t::adjust_and_emit_rseq_buffer(raw2trace_thread_data_t *tdata, addr_t
{
if (!tdata->rseq_want_rollback_)
return true;
log(4, "--- Rseq region exited at %p ---\n", next_pc);
log(4, "--- Rseq region %p-%p exited at %p ---\n", tdata->rseq_start_pc_,
tdata->rseq_end_pc_, next_pc);
if (verbosity_ >= 4) {
log(4, "Rseq buffer contents:\n");
for (int i = 0; i < static_cast<int>(tdata->rseq_buffer_.size()); i++) {
Expand Down

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